When exporting a Summary in PDF, the fields that have no values are displayed with "<Undefined>" as a value (at least "<indéfini>" in French).
Sometimes objects have really few fields with values; and it is not ecologically friendly to print pages of "Undefined", that are in fine useless.
I don't think it could be a big work to make the PDF output filtering NULL datas and not put them in PDF.
What do you think about that ?
You can choose to exclude these values from a setting in the display (Display settings > Display empty values?)